The questions of whether war is inevitable is one which has concerned many of the worlds g

here were great migrations of Rocky Mountain locusts (Melanoplus spretus). Great migrating hordes of these insects once darkened the skies on the plains east of the Rockies where crops were often destroyed; the worst years were those from 1874 to 1877. One of these migrating swarms was estimated to contain 124 billion locusts. During another migration in Nebraska it was estimated that the swarm of locusts averaged half a mile high and was 100 miles wide and 300 miles long. Usually, these swarms take off from the ground against the wind, but, once airborne, they turn and fly with it. Warm convection (对流) currents help to lift them, often to great heights. During the great locust plagues the situation in Nebraska became so serious that the original state constitution had to be rewritten to take care of the economic problems. The new document was known as "The Grasshopper Constitution". It is now believed that these locusts were a migratory form. or phase of the lesser migratory locust, which is still common there. In this respect, the North American migratory locusts resemble their African relatives. In both regions the migratory forms arise as a result of crowding and climatic factors. Migratory forms are apparently natural adaptations which bring about dispersal when locust populations become too crowded. Fortunately for our farmers, the migratory form—the so called spretus species—no longer seems to occur regularly, although there was a serious outbreak as late as 1938 in midwestern United States and Canada. Actually, there is no reason why the destructive migratory form. might not again appear if circumstances should become favorable.

Which of the following is the best title for the passage?

A．The Life Cycle of Locusts.

B．Migratory Locusts in the United States.

C．Locust Plagues in Nebraska.

D．The Reproductive Capability of the Locust.

as a severe shock to the patient and his family. Despite modern advances most people still have an irrational fear of hospitals and anaesthetic. Patients do not often believe they really need surgery—cutting into a part of the body as opposed to treatment with drugs. In the early years of this century there was little specialization in surgery. A good surgeon was capable of performing almost every operation that had been devised up to that time. Today the situation is different. Operations are now being carried out that were not even dreamed of fifty years ago. The heart can be safely opened and its valves repaired. Clogged blood vessels can be cleaned out, and broken ones mended or replaced A lung, the whole stomach, or even part of the brain can be removed and still permit the patient to live a comfortable and satisfactory life. However, not every surgeon wants to, or is qualified to carry out every type of modern operation. The scope of surgery has increased remarkably in this century. Its safety has increased too. Deaths from most operations are about 20% of what they were in 1910 and surgery has been extended in many directions, for example, to certain types of birth defects in newborn babies, and, at the other end of the scale, to life-saving operations for the octogenarian (80岁至89岁之间的人). Many developments in modern surgery are almost incredible. They include the replacement of damaged blood vessels with simulated ones made of plastic; the replacement of heart valves with plastic substitutes; the transplanting of tissues such as the lens of the eye; the invention of the artificial kidney to clean the blood of poisons at regular intervals and the development of heart and lung machines to keep patients alive during very long operations. All these things open a hopeful vista for the future of surgery.

Most people are afraid of being operated on______.

A．in spite of improvements in modern surgery

B．because they think modern drugs are dangerous

C．because they do not believe they need anaesthetic

D．unless it is an emergency operation

of a new system of radar that makes use of a beam of light is said to be ten thousand times more accurate than the best comparable system of radar that uses microwaves. The model has shown that this radar system (known as laser-doppler radar) can measure with absolute precision speeds varying from spaceship orbital injection velocities (速度) of five miles per second down to virtual stops—speeds of less than one ten thousandth of an inch per second. According to the scientists who are developing this system, such fine measures of velocity are of prime importance in space missions. In a rendezvous (会合, 会合点) between two spaceships, or in a landing approach by a vehicle onto an orbiting space station, a bump could rip open a ships skin, or a nudge (轻触) could knock the station out of its orbit. The light-beam radar, which operates at a frequency of trillions of cycles per second, could easily detect and measure the movement of a vehicle edging up to a satellite space station even at a small fraction of an inch per second. A control system using so precise a signal as this would allow a huge vehicle to dock at a space station as lightly as a feather.

Laser-doppler radar makes use of______.

A．light

B．microwaves

C．sound waves

D．both A and B

there are no other snakes at all. The adder is also the only British snake with a poisonous bite. It can be found almost anywhere, but prefers sunny hillsides and rough open country, including high ground. In Ireland there are no snakes at all. Most people regard snake bites as a fatal misfortune, but not all bites are serious, and very few are fatal. Sometimes attempts at emergency treatment turn out to be more dangerous than the bite itself, with amateurs heroically (英雄地)，but mistakenly trying to do-it-yourself surgery and other unnecessary measure. All snakes have small teeth, so it follows that all snakes can bite, but only the bite of the adder presents any danger. British snakes are shy animals and are far more frightened of you than you could possibly be of them. The adder will attack only if it feels threatened, as can happen if you take it by surprise and step on it accidentally, or if you try to catch it or pick it up, which it dislikes intensely. If it hears you coming, it will normally get out of the way as quickly as it can, but adders cannot move very rapidly and may attack before moving if you are very close. The effect of a bite varies considerably. It depends upon several things, one of which is the body weight of the person bitten. The bigger the person, the less harmful the bite is likely to be, which is why children suffer far more seriously from snake bites in Britain and though the bites can make some people very ill, there are probably just as many cases of bites having little or no effect, as there are of serious illness.

Adders are most likely to be found______.

A．in shady fields in England

B．on uncultivated land throughout Britain

C．in Scotland and nowhere else

D．in wilder parts of Britain and Ireland

ne of them was Paul Revere, a silver worker. He lived in Boston many years ago during the time when many people in the British colonies in America felt that they were being used for Britains gain. They felt that they were being taxed without fair representation in the British government. The people of Boston were especially angry, and additional British troops had been sent there to keep the excited colonists under control. Paul Revere was one of those who believed that the British would soon be on the march against the villages and farms near Boston. On the night of the eighteenth of April, 1775, Revere rowed across the Charles River to a place opposite Boston where his saddled horse was ready to ride. If the British soldiers came, he was to ride to warn the people. A friend in Boston was hidden near the British troops in a place where he could watch what they did. If they marched by land, he was to hang one lantern (灯笼) high in the tower of the old North Church in Boston where Paul could see it. If they came by sea, he would hang up two lanterns. Toward morning Revere saw two lights in the tower. The British must be coming by sea! He jumped on his horse and rode through the countryside before dawn in order to warn the farmers and villagers that they must fight at the daybreak. He rode all night and in the morning, by the time the troops arrived, the farmers were hidden all along the roads with their guns loaded. When the British came, the Americans drove them back. These first battles of the American Revolution were fought at Concord and at Lexington, Massachusetts, on April 19, 1775. In 1776 the colonies signed a declaration of independence.

What is the authors main purpose in the passage?

A．To provide information about the childhood of Paul Revere.

B．To discuss the war between the British and the Americans.

C．To tell the reader a story about Paul Revere in the American Revolution.

D．To describe the courage of the farmers and villagers in the American Revolution.

in a cycle of about twelve-and-a-half hours—just different enough from the daily cycle of the sun so that there can be no regular relationship between the shore being alternately wet and dry and alternately light and dark. The extent of the tides varies greatly, from as little as one foot in inland seas like the Mediterranean, to fifty feet or so in the Bay of Fundy in Nova Scotia. In some parts of the world, one of the two daily tides rises higher and falls lower than the other; and tides at the time of new moon and full moon are generally greater than at other times. The extent of the intertidal zone thus varies from day to day as well as from place to place. The kinds of organisms living in the region between the tidal limits depend very much on whether the shore is rocky, sandy, or muddy. Rocky shores have the most obviously rich faunas (某地区所有的动物)，because of the firm anchorage for both animals and plants, and because of the small pools left by the retreating seas. Sandy shores, especially when exposed to surf (as they usually are), have the fewest kinds of animals.

Which of the following factors does not affect the extent of the tides?

A．The composition of the shore soil.

B．The moon.

C．Time.

D．Place.

older than Edwards son. You might imagine that Caspar was raised to be an adventurous thinker, but the de Bono name was so famous, Caspars parents worried that any time he would say something bright at school, his teachers might snap (不耐烦地说), "Where do you get that idea from?" "We had to be careful and not overdo it," Edward admits. Now Caspar is at Oxford—which once looked unlikely because he is also slightly dyslexic (诵读困难). In fact, when he was applying to Oxford, none of his school teachers thought he had a chance. "So then we did several thinking sessions," his father says, "using my techniques and, when he went up for the exam, he did extremely well. " Soon after, Edward de Bono decided to write his latest book, Teach Your Child How to Think, in which he transforms the thinking skills he developed for brainstorming businessmen into informal exercises for parents and children to share. Thinking is traditionally regarded as something executed in a logical sequence, and everybody knows that children arent very logical. So isnt it an uphill battle, trying to teach them to think? "You know," Edward de Bono says, "if you examine peoples thinking, it is quite unusual to find faults of logic. But the faults of perception are huge! Often we think ineffectively because we take too limited a view. " Teach Your Child How to Think offers lessons in perception improvement, of clearly seeing the implications of something you are saying and of exploring the alternatives.

What is true about Caspar?

A．He is Edward"s son.

B．He is an adventurous thinker.

C．He first described lateral thinking.

D．He is often scolded by his teacher.

o rural America bring "big city" demands that small towns cannot afford. The following cases describe some typical towns: Retired city people moving to Kimberling City often see wildlife close to their homes. Kelly and Bette Edgington, for example, see deer on their property. Also, they have identified more than one hundred kinds of birds around their comfortable home in the small, but fast-growing retirement town in the Ozark Mountains. Yet most of the retired people heading for beautiful rural places like this one enjoy being close to some of the convenience and activities of the cities. Kimberling has a small shopping center, a country club and a golf course. It is less than twenty miles from the School of the Ozarks, which has cultural events. Kimberling City had only about 600 people in 1970 but has nearly doubled since then. A local planning official estimates the towns population will reach 4 000 by the end of the 20th century. The newcomers are demanding more paved roads, says Mrs. Edgington, the $ 50-a-month mayor. A central sewer system is needed. These services require more money, but the town does not receive enough money from taxes. Even though industries could help provide taxes to pay for these services, the town is not seeking industries. Residents do not want industries and the traffic they bring. Most residents came to get away from the cities, and now they find the town has changed. "I came here to get away from Kansas City," says retired James Mitchell. "This was really rural when I came. Now its getting crowded. "

From the passage we know that residents living in the small town now______.

A．are satisfied with their present situation

B．regret their coming

C．are to leave

D．have complaints

o and, fortunately, the number of such reasons is small. Pruning involves the cutting away of overgrown and unwanted branches, and the inexperienced gardener can be encouraged by the thought that more damage results from doing it unnecessarily than from leaving the tree to grow in its own way. First, pruning may be done to make sure that trees have a desired shape or size. The object may be to get a tree of the right height, and at the same time to help the growth of small side branches which will thicken its appearance or give it a special shape. Secondly, pruning may be done to make the tree healthier. You may cut out diseased or dead wood, or branches that are rubbing against each other and thus causing wounds. The health of a tree may be encouraged by removing branches that are blocking up the centre and so preventing the free movement of air. One result of pruning is that an open wound is left on the tree and this provides an easy entry for disease, but it is a wound that will heal. Often there is a race between the healing and the disease as to whether the tree will live or die, so that there is a period when the tree is at risk. It should be the aim of every gardener to reduce that risk of death as far as possible. It is essential to make the wound on the tree which has been pruned smooth and clean for healing will be slowed down by roughness. You should allow the cut surface to dry for a few hours and then paint it with one of the substances available from garden shops produced especially for this purpose. Pruning is usually done in winter, for then you can see the shape of the tree clearly without interference from the leaves and it is. too very unlikely that the cuts you make will bleed. If this does happen, it is, of course, impossible to paint them properly.

Pruning is probably usually done to______.

A．make the small branches thicker

B．get rid of the small branches

C．improve the shape of the tree

D．make the tree grow taller

oisy motel room, but her sleeping did not improve at home. Instead of her usual six to seven hours a night, the 37-year-old teacher slept just three or four. "Id toss and turn for hours, then get up and pace," she says. Nancy tried going to bed earlier, but the slightest noise, even her husbands breathing, disturbed her. She drank a glass of wine at bed-time and fell asleep immediately, but was awake two hours later. Her doctor prescribed a sleeping pill for two weeks. When she stopped taking the pills, though, she slept worse than ever. Most of us have the occasional short period of troubled sleep and then return to normal a few nights later. However, for one in six people insomnia is a continual problem. Now the Johns Hopkins Sleep Disorders Center in Baltimore has developed a nine-step treatment to help insomniacs cure themselves. It is based on the idea that by deliberately reducing time in bed and by modifying your waking activities you will be able to sleep more soundly. Psychologist Richard Alien, co-director of the Johns Hopkins Center, considers insomnia a 24-hour disorder. Thus, his treatment, which draws on research done by Arthur Spielman of the Sleep Disorders Center of the City College of New York, includes advice on daytime as well as bedtime behavior.

What is the subject of the passage?

A．Johns Hopkins Sleep Disorders Center.

B．Nancy Jeschke"s sleeping problems.

C．Treating the sleeping problems.

D．The relationship between noise and insomnia.